Spectral, thermal and electrochemical investigation of carbohydrazone derived ionophore as Fe(III) ion selective electrode

Article abstract of DOI:10.1016/j.saa.2013.01.055

Dibenzoylmethane bis(carbohydrazone) (BMBC) has been synthesized and structurally characterized on the basis of IR, ¹H NMR, mass, UV spectra and thermogravimetric analyses. BMBC has been analysed electrochemically and explored as new N, N Schiff base. It plays the role of an excellent ion carrier in the construction of iron(III) ion selective membrane sensor. This sensor shows very good selectivity and sensitivity towards iron ion over a wide variety of cations, including alkali, alkaline earth, transition and heavy metal ions. The response mechanism was discussed in the view of UV-spectroscopy and Electrochemical Impedance Spectroscopy (EIS). The proposed sensor was successfully used for the determination of iron in different samples.

Full text of DOI:10.1016/j.saa.2013.01.055

Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 107 (2013) 271–279
Contents lists available at SciVerse ScienceDirect
Spectrochimica Acta Part A: Molecular and
Biomolecular Spectroscopy
journal homepage: www.elsevier.com/locate/saa
Spectral, thermal and electrochemical investigation of carbohydrazone
derived ionophore as Fe(III) ion selective electrode
Sulekh Chandra a, , Deepshikha a,b, Anjana Sarkar b
⇑
a Department of Chemistry, Zakir Husain Delhi College, University of Delhi, New Delhi 110 002, India
b School of Applied Sciences, Netaji Subhas Institute of Technology, University of Delhi, New Delhi 110 002, India
g r a p h i c a l a b s t r a c t
h i g h l i g h t s
"
Carbohydrazone derivative as
ionophore has been synthesized and
characterized.
"
"
It has been explored as Fe(III) ion
selective electrochemical sensor.
The reaction mechanism was
discussed in the view of UV and EI
Spectroscopy.
a r t i c l e i n f o
a b s t r a c t
Article history:
Dibenzoylmethane bis(carbohydrazone) (BMBC) has been synthesized and structurally characterized on
the basis of IR, 1H NMR, mass, UV spectra and thermogravimetric analyses. BMBC has been analysed elec-
trochemically and explored as new N, N Schiff base. It plays the role of an excellent ion carrier in the con-
struction of iron(III) ion selective membrane sensor. This sensor shows very good selectivity and
sensitivity towards iron ion over a wide variety of cations, including alkali, alkaline earth, transition
and heavy metal ions. The response mechanism was discussed in the view of UV-spectroscopy and Elec-
trochemical Impedance Spectroscopy (EIS). The proposed sensor was successfully used for the determi-
nation of iron in different samples.
Received 22 November 2012
Received in revised form 21 January 2013
Accepted 23 January 2013
Available online 1 February 2013
Keywords:
Dibenzoylmethane bis(carbohydrazone)
Thermogravimetric analyses
Selectivity
Ó 2013 Elsevier B.V. All rights reserved.
Interaction mechanism
Ion selective sensor
Electrochemical impedance spectroscopy
Introduction
response, easy preparation, simple instrumentation, wide linear
dynamic range, relatively low detection limit, reasonable selectiv-
The development of selective chemical sensors has received
widespread attention during the past two decades because of their
possible use in clinical and environmental monitoring [1–5].
Potentiometric detection based on ion-selective membrane elec-
trodes, as a simple method, offers several advantages such as fast
ity, application in colour and turbid solutions and low cost. As a re-
sult of extensive research in this area, a number of Ion Selective
Electrodes (ISEs) mainly for alkali, alkaline earth and some heavy
and transition metal ions are now commercially available [6–9].
ISEs have found wide spread use for the direct determination of
ionic species in complex samples [10]. In the early days, their
selectivity was often the limiting factor in determining low levels
of analyte ions. In unbuffered samples, the current polymer
⇑
Corresponding author. Tel.: +91 011 22911267; fax: +91 11 23215906.
E-mail addresses: schandra_00@yahoo.com (S. Chandra), deepshikha.research@
gmail.com (Deepshikha).
1386-1425/$ - see front matter Ó 2013 Elsevier B.V. All rights reserved.
http://dx.doi.org/10.1016/j.saa.2013.01.055

272
S. Chandra et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 107 (2013) 271–279
membranes ISEs show lower detection limits that are much,
typically in the micromolar range [11].
to one end of a ‘‘Pyrex’’ glass tube. The membrane was studied un-
der polarized optical microscope (Fig. 1).
Based on above considerations, the aim of the present work is to
synthesize a neutral Schiff base ligand dibenzoylmethane bis(car-
bohydrazone) (BMBC) and characterize it on the basis of spectral
and thermal techniques. The ion receptor characteristics of BMBC
were evaluated by its application as the potentiometric sensor of
iron ions [12].
Equilibration of membrane and potential measurement
The time of contact and concentration of equilibrating solution
were optimized so that the sensors generated stable and reproduc-
ible potential at relatively short response time.
The Schiff base BMBC was used to construct iron(III) ion selec-
tive sensor. A deficiency of iron limits oxygen delivery to cells,
resulting in fatigue, poor work performance, and decreased
immunity [13–17,18]. On the other hand, excess amounts of iron
can result in toxicity and even death [19]. High levels of iron are
associated with an increased risk of cancer, heart disease and other
illnesses such as haemochromatosis [20–22]. Therefore, there is an
urgent need to design such compounds which can monitor the le-
vel of iron in the environment.
The polymeric membrane electrode was equilibrated for
ꢀ2 days in 1.0 ꢁ 10ꢂ1 M Fe(NO3)3 solution. The potentials were
measured by varying the concentration of Fe(NO3)3 in test solution
in the range 1 ꢁ 10ꢂ9–1.0 ꢁ 10ꢂ1 M. Standard Fe(NO3)3 solutions
were obtained by gradual dilution of 10ꢂ1 M Fe(NO3)3 solution.
The emf measurements with the polymeric membrane elec-
trode were carried out on digital potentiometer at 25 1 °C using
saturated calomel electrode (SCE) as reference electrode with the
following cell assemblies:
Hg–Hg2Cl2, KCl (sat.) ||internal solution 1.0 ꢁ 10ꢂ1 M Fe3 |test
solution|| Hg2Cl2–Hg, KCl (sat.)
Experimental
Materials
Physical measurements
Analytical reagent grade chemicals and doubly distilled water
were used. Dibenzoyl methane, carbohydrazide, high molecular
weight poly (vinylchloride) powder (PVC), dibutyl phthalate
(DBP), diisooctyl sebacate (DOS), tributyl phthalate (TBP) and tet-
rahydrofuran (THF) were obtained from Sigma. Potassium tetra-
kis(4-chlorophenyl)borate and 2-nitrophenyl octyl ether (NPOE)
were obtained from Fluka. Salts of metal nitrates or chlorides
and solvents like methanol, ethanol, diethylether, acetonitrile, ni-
tric acid and hydrogen peroxide (all from Merck) were of the high-
est purity available and used without any further purification. All
the metal nitrate solutions were freshly prepared by accurate dilu-
tion from their stock solution of 1 M, with distilled, de-ionized
water.
IR spectra (KBr pellets) were recorded in the region 4000–
400 cmꢂ1 on a FT–IR spectrum BX-II spectrophotometer. 1H NMR
spectrum was recorded with a model Bruker Advance DPX-300
spectrometer operating at 300 MHz using DMSO-d6 as a solvent
and TMS as an internal standard. Electron impact mass spectrum
was recorded on JEOL, JMS, DX-303 mass spectrometer. Electronic
spectra were recorded on Shimazdu UV mini-1240 spectrophotom-
eter using DMSO as a solvent. Elemental analyses were carried out
on a Carlo-Erba EA 1106 analyzer. The emf measurements with the
polymeric membrane electrode were carried out on digital
potentiometer (Equiptronic Model No. EQ-609) at 25 1 °C using
saturated calomel electrode (SCE) as reference electrode. Electro-
chemical impedance measurements were carried out using a
potentiostat/galvanostat instrument (Autolab PGSTAT 302).
Synthesis of ionophore dibenzoylmethane bis(carbohydrazone)
(BMBC)
Results and discussion
An aqueous ethanolic solution of carbohydrazide (0.02 mol,
1.80 g) was treated with 1 ml glacial acetic acid followed by slow
addition of a solution of dibenzoylmethane (0.01 mol, 2.24 g) in
20 ml ethanol. The resulting mixture was heated under reflux for
about 6 h. On cooling overnight at 0 °C, white crystalline precipi-
tate of BMBC was separated out, which was filtered, washed with
cold ethanol and dried under vacuum. Yield 81%, m.p. 182–
185 °C. Elemental analysis: C17H20N8O2, Found (Calc.) C: 55.44
(55.13), H: 5.43 (5.08), N: 30.43 (30.17).
The analytically pure ligand BMBC was readily synthesized with
very good yield (81%) by Schiff base condensation of dibenzoylme-
thane with two equivalents of carbohydrazide in water–ethanol.
The ligand may show keto–enol tautomerism because it contains
the amide bonds (Fig. 2). The IR spectrum does not show a
band at ca. 3550 cmꢂ1 but shows the bands at 3395 and
3212 cmꢂ1 corresponding to
as(NH) and s(NH), indicating that
in solid state, the ligand exists in the keto form. However, the 1H
NMR spectrum of ligand exhibits a sharp singlet at 8.1 ppm
t(OH)
t
t
t
due to enolic AOH which indicates that the amide groups are
transformed into iminol groups in solution.
Fabrication of electrodes with ionophore BMBC
For analytical application, the membranes have been fabricated
as suggested by Craggs et al. [23] and others [24]. The PVC-based
membranes have been prepared by dissolving appropriate
amounts of BBC, anionic additive and plasticizers, DBP, o-NPOE,
DOS, TBP and PVC in THF (ꢀ5 ml). The components were added
in terms of weight percentages. The homogeneous mixture was ob-
tained after complete dissolution of all the components, concen-
trated by evaporating THF and it has been poured into
polyacrylate rings placed on a smooth glass plate. The viscosity
of the solution and solvent evaporation was carefully controlled
to obtain membranes with reproducible characteristics and uni-
form thickness otherwise the response of the membrane sensors
have shown a significant variation. The membranes of 0.4-mm
thickness were removed carefully from the glass plate and glued
Fig. 1. Membrane picture under polarized optical microscope (A) before use and (B)
after use.

S. Chandra et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 107 (2013) 271–279
273
N
O
N
HN
NH
O
N
N
H
H
NH2
H2N
N
N
N
N
HN
N
NH
NH
OH
OH
O
O
N
N
N
N
H
H
H
NH2
NH2
H2N
NH2
N
N
N
N
N
N
HN
NH
OH
OH
HO
HO
HN
NH
N
N
NH2
NH2
NH2
H2N
Fig. 2. Five possible isomeric forms of ligand BMBC.
IR Spectra
1H NMR spectra
The assignments of the main IR absorption bands of the li-
gand are shown in Fig. 3. The IR spectrum of the free ligand dis-
plays the bands at 3395 and 3212 cmꢂ1corresponding to the
The 1H NMR spectrum of ligand was recorded in deuterated
DMSO (DMSO-d6) at 300 MHz. The spectrum (Fig. 4) shows that
the different non-equivalent protons resonate at different values
of applied field. A singlet at d 1.6 ppm appears due to the two
protons of methylene group. A distorted singlet at d 4.0 ppm ap-
pears in the spectrum which is assigned to the four protons of
two amino groups. The appearance of signal as a broad peak
may be due to the nuclear quadrupole broadening by nitrogen
[27]. Another distorted singlet at d 5.8 ppm corresponding to
the 2H is appeared due to the amide protons. The spectrum
tas(NH2) and ts(NH2) stretching vibrations, respectively, which
suggests the presence of free NH2 groups in the ligand. The
spectrum exhibits the IR bands at 1630 and 1617 cmꢂ1
1500 cmꢂ1 which may be assigned to the amide I [
t
(C@O)],
amide II [
t (C@N) + t (NH)] and amide III stretching vibrations,
respectively, due to the presence of the amide groups in the
ligand [25,26].

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S. Chandra et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 107 (2013) 271–279
Fig. 3. IR Spectra of ligand BMBC.
Fig. 4. 1H NMR Spectra of ligand BMBC.
exhibits a multiplet between d 6.8 and d 7.9 ppm equivalent to
the 10H of two phenyl groups. The spectrum displays a sharp
singlet at d 8.1 ppm equivalent to 2H represents the enolic pro-
tons of ligand in solution [28].
Mass spectra
The mass spectrum of ligand is given in Fig. 5. The spectrum
shows the molecular ion peak (M+) at m/z = 368 (78%) and a weak

S. Chandra et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 107 (2013) 271–279
275
Fig. 5. Mass spectra of ligand BMBC.
peak at m/z = 369 due to 13C isotope. The amide characteristic peak
Complexation study
appears at m/z = 59 and the moderate high intense peak (81%) at
m/z = 177 appears in the spectrum due to the six member cyclic
The interactions between the ionophore (L) and different tran-
sition metals were tested. Thus, the complexation behaviour of L
with different cations was measured conductometrically in aceto-
nitrile solution, at room temperature in order to establish the sta-
bility and sensitivity of the resulting complexes. The 1:1 binding of
the cations with the ionophore can be expressed by the following
equilibrium
positive ion which results from
c d CAC bond cleavage and fol-
lowed by cyclisation. The other different ions give the peaks of dif-
ferent mass numbers like 309, 190.9, 132, 119 and 55. The
intensities of peaks are in accordance with the abundance of the
ions [29]. The fragmentation path of ligand is given in Fig. 6.
M
nþ þ L ꢀ MLnþ
ð1Þ
Thermogravimetric analyses
The complex formation constant, Kf were evaluated by the molar
conductance mole ratio data obtained by using the equations given
below:
BMBC was studied by thermogravimetric analyses from ambi-
ent temperature to 700 °C in nitrogen atmosphere. The TG curve
was redrawn as % mass loss versus temperature (TG) curve. Typical
TG curve is presented in Fig. 7. Thermal techniques, such as ther-
mogravimetric analysis (TG and DTG), has been successfully em-
ployed for the study of the energetic of interactions of metal
cations with biological species, such as amino acids [30]. The
weight loss profiles are analysed the amount or percent of weight
loss at any given temperature, and the temperature ranges of the
degradation process were determined. Thermal stability domains,
melting points, decomposition phenomena and their assignments
for the BMBC are summarized below. The overall loss of mass from
the TG curves is 100% for BMBC. The compound is stable up to the
temperature 300 °C. The compound undergoes first step decompo-
sition with weight loss exp. 4.335–4.658%, between 130 and 168 °C
due to the loss of NH2 moiety. Delta H for the degradation is
112.082 J/g. DTG maximum temperature is 202.16 °C and it shows
an endo peak.
½MLnþꢃ
nþÞ
fðML
Kf ¼
ꢁ
¼
ð2Þ
½Mnþꢃ½Lꢃ
nþ
fðM fL
Þ
½MLnþꢃ
KM
ꢂ
Kobs
KMLÞL
Kf ¼
ð3Þ
ð4Þ
½Mnþꢃ½Lꢃ
ð
Kobs
ꢂ
CMðKM
ꢂ
Kobs
Þ
Kf ¼ CL ꢂ
Kobs
ꢂ
KML
where [MLn+], [Mn+] and [L] represents equilibrium molar concen-
tration of complexes, free cation and free ligand respectively. KM
is the molar conductance of the cation before addition of the ligand,
KM is the molar conductance of the complex, Kobs molar conduc-
tance of the solution during titration and
K is the analytical concen-
tration of the ionophore. The complex formation constant Kf and the

276
S. Chandra et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 107 (2013) 271–279
.
O
.
R1
m/z=59
C
N
H
NH2
N
O
N
HN
NH
H
N
N
O
O
.
R2
N
N
.
N
H
H
NH2
H2N
H
H3N
m/z=368
H
N
NH2
N
N
O
.
N
H
N
m/z=119
H2
.
NH
N
O
N
m/z=177
HN
m/z=309
N
H
H2N
.
m/z=77
.
.
N
O
NH3
N
HN
m/z=132
.
N
N
NH
H
H2N
m/z=55
m/z=191
Fig. 6. Mass fragmentation pattern of ligand BMBC.
molar conductance of the complexes were obtained by using a
non-linear least square program KINFIT [31]. In this experiment,
the ligand to cation mole ratio was equal to 1 in all cases. The for-
mation-constant values (log Kf = 5.92 0.12) of the resulting 1:1
complexes in Table 1 show the high selectivity of the proposed ion-
ophore to Fe3+ ions. The suggested structure of Fe3+ complex with
BMBC is shown in Fig. 8.
Electrochemical sensor
Response of electrode based to Fe3+ ions
The existence of nitrogen and oxygen as donor atoms in the
ligand with high lipophilic character seems to form strong com-
plexes with transition metal ions [25,26,29]. In order to study the
potential response and selectivity of the ionophore for different

S. Chandra et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 107 (2013) 271–279
277
Fig. 7. TGA/DTA curve for ionophore BMBC.
Table 1
metal ions, BMBC was used as a neutral carrier to prepare PVC
based membrane electrodes for a variety of metal ions including
alkali, alkaline earth, transition and heavy metal ions. The potential
responses obtained are shown in Fig. 9. The sensitivities and
selectivites obtained for a given membrane depend significantly
on the membrane ingredients and the nature of plasticizer and
additives used. Therefore, 10 membranes of different compositions
(Table 2) have been prepared and their response characteristics
were evaluated according to the IUPAC recommendations [32].
The best performance was obtained with a membrane composi-
tion of 31% poly (vinyl chloride), 64% DOS, 3.5% BMBC and 2%
Potassium tetrakis(4-chlorophenyl)borate. The electrode exhibits
a Nernstian behaviour (with slope of 19.7 mV per decade) over a
Stability formation constants of different metal ions with BMBC.
Metal
log Kf
Metal
log Kf
Fe3+
Zn2+
Cr3+
La3+
Mn2+
Pb2+
Fe2+
5.92 0.2
Hg2+
Co2+
Ni2+
Cu2+
Ag+
1.49 0.03
2.57 0.07
1.98 0.08
3.45 0.02
1.99 0.02
2.12 0.05
2.35 0.02
1.47 0.04
3.45 0.03
2.98 0.03
2.12 0.04
1.14 0.02
3.42 0.01
Cd2+
Bi3+
H2
C
NO3
N
N
HN
NH
Fe
O
O
NO3
NH
NH
NH2
Fig. 8. Suggested structure of Fe(III) complex of BMBC.
H2N
Fig. 9. Potential response of ligand BMBC to Mn+ ion.

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S. Chandra et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 107 (2013) 271–279
very wide concentration range 1.0 ꢁ 10ꢂ3–1.0 ꢁ 10ꢂ9 M with a
detection limit of 3.2 ꢁ 10ꢂ9 M. This sensor shows very good selec-
tivity and sensitivity towards iron ion over a wide variety of cat-
ions, including alkali, alkaline earth, transition and heavy metal
ions. In this work, the selectivity coefficient of the sensor towards
different cationic species (Mn+) was evaluated by using the fixed
interference method (FIM) [33,24]. In FIM, the selectivity coeffi-
cient was evaluated from potential measurement on solutions con-
taining a fixed concentration of interfering ion (1.0 ꢁ 10ꢂ2 M) and
varying amount of Fe3+ ions. It is given by the expression
Table 3
ꢀ
ꢁ
pot
Fe3þ ;B
Potentiometric selectivity coefficient log K
for interfering ions.
pot
pot
Interfering ion
Interfering ion
log K
log K
Cd2þ;B
Cd2þ ;B
K+
ꢂ2.65
ꢂ3.47
ꢂ2.21
ꢂ2.98
ꢂ3.03
ꢂ2.87
ꢂ3.32
ꢂ2.34
Cr3+
Zn2+
Pb2+
Sr2+
ꢂ3.32
ꢂ2.38
ꢂ3.51
ꢂ3.27
ꢂ2.82
ꢂ3.19
ꢂ3.84
ꢂ3.59
Ba2+
Cs+
Ni2+
Cu2+
Co2+
La3+
Fe2+
Hg2+
Ce3+
Ca2+
Mg2+
ZFe3þ =ZB
pot
Fe3þ;B
log K
¼ logðaFe3þ Þ ꢂ logðaBÞ
3þ
where Z and ZB is the charge on Fe3+ ion and interfering ion.
Fe
pot
Fe3þ;B
The resulting K
values are summarized in Table 3 and
shows that BMBC sensor is highly selective to iron ions in presence
of various ions.
The effect of pH of the test solution on the response of the mem-
brane electrode was examined at two Fe3+ ion concentrations. As
illustrated in Fig. 10, the potentials remained constant from pH
2.6 to 6.6. However, outside this range the electrode responses at
pH < 2.6 seems ascribable to the competitive binding of proton to
the ligand at the surface of the membrane electrode, while the
diminished potential at higher pH (>6.6), the potential change
may be due to the hydroxylation of Fe3+ ions.
Dynamic response time is an important factor for any ion-selec-
tive electrode. In this study, the practical response time was re-
corded by immediately changing the Fe3+ ion concentration from
1.0 ꢁ 10ꢂ9 to 1.0 ꢁ 10ꢂ3 M. In the whole concentration range, the
sensor reaches the equilibrium response in a very short time
(ꢀ9 s).
Fig. 10. pH effect on the response of Fe3+-ISE.
characteristic towards Fe3+. This sensor has potential applications
in a variety of fields. We successfully applied the ionophore elec-
trode as an indicator electrode in the potentiometric titrations as
well as determination of iron(III) ion in various water samples
and in ferric tablets. The results obtained were in good agreement
with atomic absorption spectroscopy results shown in Table 4.
To evaluate the reversibility of the electrode, a similar proce-
dure in the opposite direction was adopted. The measurements
have been performed in the sequence of high-to-low from
(1.0 ꢁ 10ꢂ3–1.0 ꢁ 10ꢂ9 M) sample concentrations. The results
showed that, the potentiometric response of the electrodes was
reversible; although the time needed to reach equilibrium values
(40 s) were longer than that of low-to high sample concentrations.
The high lipophilicity of ionophore and plasticizer ensure table
potentials and longer lifetime [24] for the membrane. Hence, the
lifetime is dependent upon the components of the solution and
the measured specimens. The lifetime of the electrode was deter-
mined by performing calibrations periodically with standard solu-
tions and calculating the slopes over the concentration ranges of
1.0 ꢁ 10ꢂ3–1.0 ꢁ 10ꢂ9 M Fe3+ solutions. The experimental results
showed that the lifetime of the present sensor was over 95 days.
During this time, the detection limit and the slope of the electrode
remained almost constant. Afterwards, the electrochemical behav-
iour of the electrode gradually deteriorated, which may be due to
ageing of the polymer (PVC), the plasticizers, and leaching of the
ionophore. Therefore, the electrode can be used for at least
Interaction mechanism on the basis of UV spectroscopy
The interaction mechanism of Fe3+ ion with the ionophore was
discussed on the basis of UV–visible spectrophotometry. Thus, in
order to investigate such mechanism of UV–visible spectra of car-
rier without and with iron ions were recorded. A UV–visible spec-
trum of BMBC of 0.001 M concentration dissolved in DMSO was
recorded first. It was then used for the quantitative complexation
Table 4
Determination of Fe(III) in different samples.
Samples
Proposed sensor (ppm) AAS (ppm)
Tap water1 (Dwarka, New Delhi)
5.9 0.1
5.7 0.2
3.5 0.2
Tap water2 (Ajmeri gate, New Delhi) 3.3 0.2
3 months without
a considerable change in their response
Table 2
Optimization of membrane composition.
S. No.
PVC (wt.%)
Plasticizer (wt.%)
Ionophore (wt.%)
KTpClPB (wt.%)
Slope (mV/decade)
Detection limit (M)
Linear range (M)
1
2
3
4
5
6
7
8
9
33
33
33
31
33
31
32
33
34
31
66(DOS)
65(DOS)
65(DOS)
64(DOS)
63(DBP)
65(NPOE)
65(TBP)
64(NPOE)
64(NPOE)
66(DBP)
1.0
1.5
1.0
3.0
3.0
3.0
2.0
1.0
2.0
1.0
–
9.6
13.2
18.1
19.7
13.5
11.3
13.7
25.4
24.6
15.6
1.0 ꢁ 10ꢂ5
1.6 ꢁ 10ꢂ5
6.0 ꢁ 10ꢂ5
3.2 ꢁ 10ꢂ9
5.0 ꢁ 10ꢂ7
1.0 ꢁ 106
1.0 ꢁ 10ꢂ3–1.0 ꢁ 10ꢂ5
1.0 ꢁ 10ꢂ2–1.0 ꢁ 10ꢂ5
1.0 ꢁ 10ꢂ3–1.0 ꢁ 10ꢂ6
1.0 ꢁ 10ꢂ3–1.0 ꢁ 10ꢂ9
1.0 ꢁ 10ꢂ1–1.0 ꢁ 10ꢂ7
1.0 ꢁ 10ꢂ4–1.0 ꢁ 10ꢂ7
1.0 ꢁ 10ꢂ3–1.0 ꢁ 10ꢂ7
1.0 ꢁ 10ꢂ1–1.0 ꢁ 10ꢂ6
1.0 ꢁ 10ꢂ1–1.0 ꢁ 10ꢂ8
1.0 ꢁ 10ꢂ4–1.0 ꢁ 10ꢂ7
0.5
1.0
2.0
1.0
2.0
1.0
2.0
2.0
1.0
5.0 ꢁ 10ꢂ6
1.0 ꢁ 10ꢂ5
3.2 ꢁ 10ꢂ8
3.0 ꢁ 10ꢂ5
10

S. Chandra et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 107 (2013) 271–279
279
Fig. 11. UV–visible interaction mechanism of (a) BMBC (1 ꢁ 10ꢂ3 M) in DMSO and (b) BMBC with Fe3+ (1 ꢁ 10ꢂ3 M) in DMSO.
sensor was used for the direct determination of iron ion in different
samples with reproducible results.
Acknowledgements
The author is thankful to the principal, Zakir Husain Delhi Col-
lege for providing the laboratory facility and Netaji Subhas Insti-
tute of Technology for financial assistance.
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Electrochemical impedance spectroscopy
Impedance measurements were carried out on the membrane
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M
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Conclusion
On the basis of IR, 1H NMR and mass spectra, dibenzoylmethane
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analysed and explored as a iron(III) ion selective electrode. The
interaction mechanism is explained by the UV-spectroscopy and
electron impedance spectroscopy. The ionophore BMBC based
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